Indicating fuse holder



Oct. 7, 1958 D. J. swme ErAL 2,855,483

INDICATING FUSE HOLDER Filed Sept. 14, 1954 v 3 vas I j 65 i I Iii. 3.

INVENTOR David J: Swing VIA. Czaw lyiho ATTORNEY- I Unite 1N DICATING FUSE HOLDER David J. Swing, Mount Rainier, and Valentine A.

Czawlytko, Baltimore, Md., assignors, by mesne assignments, to ACF Industries, Incorporated, a corporation of New Jersey Application September 14, 1954, Serial No. 455,824

7 Claims. (Cl. 200-121) This invention relates broadly to holders for fuses and, more particularly, to fuse holders which include means for indicating whether the fuse has blown.

Fuses and fuse holders having means for indicating the inoperative condition of the fuse are now known. One well-known type utilizes a resistance in parallel with the fuse and connected to an indicator such as a light. During normal operation of the fuse, current flows through the fuse but does not energize the indicator due to the intervening resistance. When the fuse blows, full line voltage overcomes the resistance and energizes the alarm. In a second type of fuse, a cartridge fuse is provided with a spring-urged plunger attached and normally retracted to the fusible element. When the fusible element melts, the plunger extends into contact with a conducting bar to transmit the full line voltage from the source through the plunger and conducting bar to the indicating means. In both of the described types of indicating fuse, full-line voltage is transmitted to the indicating means, which is dangerous to personnel servicing the fuses. Further, the indicating means and the resistances must vary with the type of voltage normally flowing through the fuse in order that the alarm systems themselves will not become overloaded and thus be de stroyed when the fuse blows. This requires a variety of different parts and is expensive. The present invention eliminates the disadvantages of known devices of the described types by providing an indicating fuse holder having indicating means which are energized from a source of energy which is completely separate fromthe main line source, and one object of the present invention is the provision of an indicating fuse holder which accomplishes this purpose.

Another object of the invention is to provide an indicating fuse holder for a cartridge fuse in which the fuse transmits the load current in the normal manner, but, when the fuse is blown, a separate circuit is operative to energize indicating means to signal the blown condition of the fuse.

Another object of the invention is to provide an indicating fuse holder for a cartridge which is relatively safe for handling by operating personnel; which is compact and inexpensive; and which is adapted for use in circuits carrying a variety of currents at varying voltages with no changes required in the holder whatsoever for any electrical condition save the provision of a fuse of proper capacity to suit any specific electrical conditions.

These and other objects and advantages will become apparent as the following description is read in conjunction with the accompanying drawing wherein:

.Fig. l is a schematic wiring diagram of an indicating fuse holder according to the present invention;

Fig. 2 is aside elevational view of an assembled indicating fuse holder according to the present invention;

Fig. 3 is a cross-sectional view of the indicating fuse holder of the present invention taken substantially on the line 33 of Fig. l and showing the interior body portion slightly withdrawn from the base member of the holder for purposes of illustration, and

Fig. 4 is a transverse cross-sectional view taken substantially on the line 44 of Fig. 3 but showing the interior body portion in its assembled position with respect to the base member.

The indicating fuse holder of the present invention is adapted for use with cartridge fuses of known commercial design which are provided with spring-urged extensible plungers normally attached in retracted position to one end of a fusible element within the cartridge. When the fuse is blown, i. e., when the fusible element melts due to an over-load or otherwise, the plunger moves to extended position to give an indication of the blown condition of the fuse. The holder provided by the present in vention is adapted for use with this type of cartridge fuse and, in addition, provides electrical indicating means which is energized by extension of the plunger. A novel feature of the invention resides in the use of an indicating circuit actuated upon extension of the plunger, which circuit is completely separate from the load circuit which includes the fuse. The separate indicating circuit of the invention may be connected to a source of low power not exceeding, for example, the power output of a single flashlight battery, while the main power circuit remains open and safe due to the blown condition of the fuse. Furthermore, unlike prior arrangements, which utilize fuses of the extensible plunger type to transmit load voltage through the plunger to the indicating means when the fuse is blown, the present invention permits the plunger end of the fuse to be connected to the load side of the load circuit so that the plunger end, when the fuse blows, is completely de-energized, the plunger thereafter acting only as a mechanical switch-actuating means to energize the indicating circuit.

Referring now to the drawing and particularly to Fig. 1 thereof, the circuits in which the holder of the present invention may be utilized are illustrated as comprising a main line circuit Iii containing a power source 11 of desired voltage connected in series through a fuse 12 to the load 13. The main line circuit may be connected to the fuse at junctions i4 and i5 and the fuse diagrammatically illustrated may be of the known commercial type having a plunger 17 constantly urged by spring 18 to extended position but maintained in a retracted position by the fusible element, to which the plunger is connected. When the fuse is blown due to an overload or otherwise the plunger 17 is released to strike against an insulated cap 19 on which is mounted an upstanding metallic extension 20. A conical spring 21 of considerably less strength than spring 18 normally retains the cap 19 in the downward position shown but when struck by plunger 17 the cap 19 moves upwardly until extension 20 strikes a contact element 22 which is connected in series with a visual alarm such as electric bulb 23 or an audible alarm such as a bell 24 or with both. When extension 26 con tacts element 22 a separate indicating circuit generally indicated by the numeral 25 is energized from a power source 26, causing visual alarm 23 to light and audible alarm 24 to ring if this latter is used in conjunction with visual alarm 23. The power source 26 of the indicating circuit may be connected at junction 29 to a laterally extending, electrically conductive, centrally apertured pin 30 through which extension 20 moves, and the conical spring 21 which is in contact at its upper end with pin 30 and at its lower end with extension 20 serves as a conducting path between these members. Visual alarm 23 may be connected to ground at junction 32 and audible alarm 24 may be connected to the contact 22 at junction 33. It should be understod that audible alarm 24 is only illustrative of one type of device which may be actuated upon blowing of the fuse and that other electrically operated signalling devices may also be energized if desired. Furthermore, it is contemplated that in lieu of, or in combination with, the alarm 24 the circuit thereof may be connected through suitable manually operated switch means back to power source 26 so that the condition of indicating bulb 23 may be tested. A double throw switch would of course be preferably to disconnect circuit 25 from pin 30 when testing bulb 23.

Referring now to Figs. 2 through 4, the holder of the present invention may comprise two principal interfitting members formed of insulating material such as hard rubber or the like and comprising an exterior base member 40 and an interior body member 41 which is shown in Fig. 3 slightly withdrawn from the base member for the purpose of illustration. The base member 40 may be of a hollow generally cylindrical construction having an integral flange 42 at the upper end thereof which may abut the face of a suitable panel board (not shown) when threads 43 are screwed into a suitably threaded aperture in the panel. The side of the base member 40 is suitably apertured for receiving the electrical connections of the load circuit and of the indicating circuit all as explained hereinafter.

The interior body member 41 is formed of insulating material and is of cylindrical shape, being of a size to fit within the bore of the base member 40. Member 41 is provided with an enlarged integral head portion 44 which abuts the bottom of a mating recess 45a in the upper flanged portion 42 of the base member 40 when members 41 and 40 are in the assembled condition shown in Fig. 2. The interior of head portion 44 is recessed to receive electric lamp 23 and the lower end of member 41 is annularly grooved at 45 to receive an upper fuse retainer 46 which may be held in groove 45 by any suitable means as by inturned fingers 47 which resiliently engage the inner wall of the groove 45 as shown.

At its lower end the member 41 has a central bore 48 which is inside and concentric with groove 45 and in which the insulated cap 19 carrying upstanding member 20 is received. Pin 30 is rigidly fixed through aligned apertures in the side of member 41 and, as shown in Fig. 3, this pin projects slightly beyond the outer wall of member 41 to form a projection which slides within elongated longitudinal part of a right-angular guide groove 49 in the interior surface of base member 40 when member 41 is placed therein for assembling. In Fig. 3 the inner body member 41 is shown not quite seated in base member 40 with the pin 30 still in the elongated portion of groove 49. When the inner member 41 is completely seated a slight twist of member 41 with respect to base member 40 moves the pin 30 into the lateral portion of groove 49 at the bottom thereof thus forming a bayonet connection between the two parts to lock the members 40 and 41 in the assembled condition shown in Fig. 2. As previously explained, pin 30 is centrally apertured to receive upstanding extension 20 and the lateral projection of the pin serves as an electrical contact member which engages an inturned portion 50 of a conductor band 51, later described, when member 41 is locked in assembled position.

The contact element 22 described hereinbefore is mounted on the lower leg of a C-shaped strip of resilient sheet material 52 fixed within the interior of member 41' by means of a conducting rivet 53 which projects through the wall of member 41 to engage an inturned portion 54 of a second conductor band 55 when the holder is assembled. The strip 52 has a resilient inwardly projecting upper leg portion 52a which engages the contact point 23a of bulb 23 as shown in Fig. 3. The circuit through the bulb to ground is completed through a metallic bulb retainer cup 56 having bayonet slots 57- in the side thereof engageable by pins 58' projecting radially from the sides of the bulb base. .Retainer cup 56 is provided with an out-turned finger 59 which projects through aligned openings 60 in the members 40, 41 beneath the head portion 44 and makes electrical contact with a conductor 61 when inner body member 41 is locked in assembled position in base member 40. Conductor 61 terminates in an 0ut-turned connector tab 32 projecting through the wall of base member 40 and corresponding to the junction 32 which may be connected to ground as shown in Fig. 1.

The described conducting bands 51 and 55 may be of identical construction and the description of the band 51 shown in Fig. 4 sufiices for both. These bands substantially'encircle the exterior of base member 40 and are held in place in any suitable manner as by the engagement of inturned flanges with the sides of suitable apertures 62 formed in the wall of the base member. The conducting bands 51, 55 are respectively provided with out-turned connecting tabs 29, 33, corresponding to junctions 29, 33 in Fig. 1 to which may respectively be connected the indicating power source 26 and audible alarm 24.

Referring to Fig. 3, the fuse 12, schematically shown in Fig. 1 is of a known cartridge type having the spring pressed extensible plunger 17 which is connected to the fusible element and held retracted thereby against the pressure of a spring 18. When the fusible element is parted due to an overload or otherwise the plunger 17 moves to extended position to strike cap 19 and energize the indicating circuit all as previously described.

The upper end of the cartridge fuse 12. is frictionally received in the retainer cup 46 which is secured to inner body member 41 as previously explained. Cup 46 in turn makes electrical contact with a cylindrical conductor 63 which is carried by the inner surface of base member 40, when the inner body member 41 is assembled to the latter. Conductor 63 has an out-bent connecting tab 15, corresponding to junction 15 shown in Fig. l, to which one side of the main load circuit is connected, the connection being preferably to the load side of the circuit for the reason previously explained above. The lower end of fuse 12 engages one end of a compression spring 64 seated in the bottom of base member 40 and adjacent its lower end the fuse electrically engages a conductor 65 having a portion 14 which projects outwardly through an aperture in the base of member 40 and corresponds to the junction 14 in Fig. 1 to which the voltage source side of the load circuit may be connected.

In operation, the fuse 12 is initially inserted into the cup of inner body member 41 and the latter is assembled to base member 40 by aligning the rivet 53 and the projecting end of pin 30 with groove 49 and then moving member 41 into base member 40 until seated, after which a slight twist of the former locks the parts of the holder together.

When the load 13 is placed on the line, current flows from the source 11 through the fuse 12 to the load in the normal manner. At the same time the separate indicating circuit is connected between the auxiliary source 26 and the pin 30 through conducting band 51. This latter circuit is open due to the depressed condition of insulated cap 19 and upstanding member 20.

When the fusible element of the fuse melts due to an overload in the load circuit, plunger 17 is released and urged by spring 18 against insulated cap 19 moving upstanding member 20 against contact element 22 thereby closing the auxiliary indicating circuit and causing visual alarm 23 to light and the remote audible alarm 24 to be energized. This last alarm serves the very useful purpose of warning operating personnel that a fuse has blown. The bank of fuses is then inspected to determine by means of the visual alarm which fuse is blown and requires replacement and since the indicating means may be connected toa source of very low power operating personnel may dissemble the holder for fuse replacement with no danger of injury from the full-line load cir cuit and without the necessity of shutting down the entire system, this being accomplished by removal of member 41 and the attached blown fuse from member 40.

Though the indicating holder of the present invention has a wide range of applicability, it is particularly useful in electrical systems utilizing a number of circuits carrying different voltages and currents for operating various pieces of equipment as, for example, in electrically operated flight simulators wherein every instrument and flight condition found in actual aircraft must be simulated. Since these may require a great number of combinations of voltages and frequencies in a complex arrangement of circuits, the indicating holder of the present invention is particularly suitable since it can be utilized in each one of the circuits without any changes between individual holders save the provision of a fuse of suitable size to protect the individual circuits. Where banks of holders are used a common, low-power, indicating circuit can be connected to the individual fuse holders in a manner well known in the art so that the alarm of indi vidual holders will be energized upon fuse failure to indicate that fact to operating personnel.

Though one embodiment of the holder of the present invention has been shown and described it will be apparent to those skilled in the art that the invention is susceptible of other embodiments without departing from the scope of the appended claims.

What is claimed is:

1. In an electrical apparatus for an alarm circuit, the combination comprising an insulating housing containing a cartridge fuse and having an extensible plunger movable to extended position upon fuse failure, terminals on said housing to connect the fuse in a main load circuit, a plurality of auxiliary terminals on said housing to connect to an auxiliary source of power and the alarm circuit, a member insulated from the main load circuit and movable to complete a connection between the said auxiliary terminals, a spring to bias said member to open position, said member being arranged in the path of motion of the fuse plunger whereby failure of the fuse releases the plunger for motion against the member to force the same to complete the connection to the alarm circuit.

2. In an electrical apparatus the combination comprising an insulating housing, a cartridge fuse in said housing and having an extensible plunger movable to extended position upon fuse failure, terminals on said housing to connect the fuse in a main load circuit, a pair of auxiliary terminals on said housing to connect to an auxiliary source of power, a lamp fixed in said housing, means to connect said lamp to said auxiliary terminals, said means including a member insulated from the. main load circuit and movable to complete a connection between the auxiliary terminals, a spring to bias said member to open position, said member arranged in the path of motion of the fuse plunger whereby failure of the fuse releases the plunger for motion against the member to move the same to complete the circuit between the auxiliary terminals.

3. An indicating fuse holder for a cartridge fuse of the type having an extensible plunger movable to extended position upon fuse failure comprising a tubular holder for the fuse having terminals for connecting the fuse in a main load circuit, a removable inner body member adapted to fit within said tubular holder having a pair of auxiliary terminals connectible in an alarm circuit, an auxiliary source of power in the alarm circuit, a bridging member insulated from said main load circuit for completing in a closed position an electrical connection between the auixilary terminals, and a spring for biasing the bridging member to a normally open position, said bridging member being disposed in the path of travel of the fuse plunger so that the bridging member is moved to the alarm circuit completing position by the plunger upon the blowing of the fuse.

4. An indicating fuse holder for a cartridge fuse of the type having an extensible plunger movable to extended position upon fuse failure comprising a tubular holder for the fuse having terminals for connecting the fuse in a main load circuit, a removable inner body member adapted to fit within said tubular holder, a pair of auto iliary terminals connectible in an alarm circuit and having an auxiliary source of power, a light within said inner body member in series with one terminal of said auxiliary terminals, a bridging member insulated from said main load circuit for completing in a closed position an electrical connection, between the auxiliary terminals, and a spring for biasing the bridging member to a normally open position, said bridging member being disposed in the path of travel of the fuse plunger so that the bridging member is moved to the alarm and light circuit completing position by the plunger upon the blowing of the fuse.

5. In an electrical apparatus, a housing, a cartridge fuse held in said housing having an extensible plunger movable to extended position upon fuse failure, a series of terminals on the housing to connect the fuse into a power circuit, an assemblage of auxiliary terminals on the housing to connect to an auxiliary power source and an alarm circuit, a member movable to complete a connection between the said auxiliary terminals, and yielding means normally urging said member to open circuit position, the said member arranged in the path of motion of the fuse plunger whereby failure of said fuse releases the plunger for motion against the said member to overcome the said yielding means and complete the alarm circuit.

6. In an electrical apparatus of the type having a housing adapted to hold a lamp and a cartridge fuse with an extensible plunger movable to extended position upon fuse failure, a pair of terminals fixed to the housing adapted to connect the respective ends of the fuse into a circuit to be protected, a pair of auxiliary terminals fixed on the housing to connect the lamp in a circuit with an auxiliary power source, a conductive member movable to bridge between conductors terminating at said auxiliary terminals, and a compression spring urging said member to open circuit position, the said conductive member being disposed in the path of the fuse plunger, whereby fuse failure releases the plunger for motion against said conductive member to compress the spring and complete the connection between the said auxiliary terminals.

7. In an electrical apparatus, a housing, a lamp held by said housing, a cartridge fuse held in said housing having an extensible plunger movable to extended position upon fuse failure, a pair of terminals fixed to the housing adapted to connect the respective ends of the fuse into a circuit to be protected, an alarm, a pair of auxiliary terminals fixed on the housing adapted to connect the alarm and lamp in circuits with an auxiliary power source, a conductive member movable to bridge between conductors terminating at the said auxiliary terminals, and a compression spring urging said member to open circuit position with said auxiliary terminals, the said conductive member being disposed in the path of the fuse plunger, whereby fuse failure releases the plunger for motion against said conductive member to compress the spring and complete the connection of said conductive member with said auxiliary terminals.

References Cited in the file of this patent UNITED STATES PATENTS 1,813,844 Gilbert July 7, 1931 1,844,030 Burno Feb. 9, 1932 2,255,470 Matthews Sept. 9, 1941 2,405,929 Wald Aug. 13, 1946 2,448,389 Powell Aug. 31, 1948 2,473,196 Dannenberg June 14, 1949 2,476,236 Buckley July 12, 1949 2,581,308 Smith Jan. 1, 1952 2,683,201 Miller et al. July 16, 1954 FOREIGN PATENTS 329,036 Great Britain May 15, 1930 

